A wireless communication service may be provided via different types of networks, e.g., LTE networks, and the like. Any number of User Equipment (UE) may communicate via each base station, e.g., an eNodeB. As the number of UEs continues to grow, there is an increasing demand for supporting data rates of hundreds of Gbps. In order to support the high data rates, communications systems with large capacity are needed. The capacity of communications systems increases linearly with the bandwidth.
One approach to support very high data rates may be to use ultra-wideband communication systems. For example, wireless networks beyond the LTE, e.g., 5G networks, may need to rely on ultra-wideband systems to deliver data rates of hundreds of Gbps. However, as the bandwidth of the communication system increases, high-speed ADCs are needed. Unfortunately, the energy efficiency of ADCs drops dramatically when the sampling rate is in excess of 100 MHz.
One approach to improve the energy efficiency is by using low-resolution ADCs. The low-resolution ADCs also reduce circuit complexity. As such, for applications that need high-speed sampling, communications systems that use very low-resolution ADCs have received increasing attention. However, once very low resolution ADCs are employed, the capacity of the communications system is fundamentally limited by a quantization level. In other words, delivering the desired data rate, while simultaneously meeting resolution and power requirements is challenging. For instance, as an example, assume a one-bit ADC is used. Then, Quadrature Phase Shift Keying (QPSK) modulation is information-theoretically optimal for a Single-Input Single-Output (SISO) fading channel. Hence, 2 bits/s/Hz is the maximum spectral efficiency for a SISO communications system using the one-bit ADC.
One approach for compensating for the limitation in the spectral efficiency is by using multiple antennas. The spectral efficiency of the communications system improves linearly with the number of receive antennas. Thus, ultra-wideband massive multiple-input multiple-output (MIMO) communication systems operating with low-resolution ADCs have a potential for being communications systems of choice for future networks. Massive MIMO systems may be designed to provide the needed high-capacity while being energy efficient. The high-capacity may be appropriate for supporting future cellular and Wi-Fi communications networks. However, conventional MIMO schemes for detecting data are developed for channels that may be expressed as linear channels. Hence, conventional MIMO schemes for detecting data are suboptimal when a low resolution ADC is used.
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